1. Field of the Invention
The present invention relates to the prevention of oil emulsification/dispersion in desalter brine water via the use of a water soluble polymer dispersed in a concentrated salt media.
2. Description of the Prior Art
In an oil refinery, the desalting process is a water extraction of crude oil in order to remove water soluble and water dispersible impurities. Crude oil is heated to a temperature of 230-300 degrees Fahrenheit. In more detail, water containing low levels of impurities is injected into the crude oil. Next, this stream of oil and water is subjected to high shear in order to thoroughly mix the wash water into the crude oil, thereby diluting the impurities. This shearing action produces a relatively stable water-in-oil emulsion. The emulsion enters a desalting vessel where the emulsion is resolved with the assistance of residence time and an electric field. Ideally, the process results in crude oil that is relatively free of water soluble impurities and a brine stream that is free of oil.
However, in most cases, chemicals are required to speed the resolution of the emulsion in order to provide oil that is relatively free of water and water that is free of oil. Such chemicals are known as emulsion breakers or demulsifiers. In some situations, refiners choose to process more crude oil than their equipment is designed to accommodate. Occasionally, the emulsion breaker cannot overcome these equipment limitations. The result is a brine stream that contains 05.-2.0 volume % dispersed oil. Often, extremely high dosages of the emulsion breaker are required to alleviate this situation.
Latex polymers suffer from problems but are used quite frequently. Latex polymer preparations include 30-35% solids dispersed in oil. The latex polymer must be also inverted prior to use. The equipment in the oil refinery for prior inversion is not always available, thus forcing the direct feeding of the polymer into the system. Numerous problems associated with this feeding method have caused many customers to avoid latex polymers. In addition, the latexes generally have a very narrow treating range, often resulting in overtreatment at higher dosages.
The oil in these systems consists of crude oil. The amount of oil in this application can range from several hundred to tens of thousands parts per million. The prevention of oil emulsions or dispersions in the desalter brine water inhibits oil loss and provides cleaner water sent to the wastewater treatment plant. The avoidance of oil being received at the wastewater treatment plant can be very critical to the established discharge limits for total dissolved solids (TSS), carbon oxygen demand (COD), biological oxygen demand (BOD) and total organic carbon (TOC) into local sewers and rivers. Not only has the EPA established severe limits on the oil and grease discharge, these industries are affected by local city ordinances as well.